Palicourea Aubl. includes in its traditional sense about 250 species of shrubs and small trees distributed widely in the New World tropics. Palicourea plants are typically found in the understory and subcanopy of moist to wet tropical forests, from low to high elevations. Palicourea flowers have well developed tubes and are odorless, mostly brightly colored, and assumed to be pollinated by hummingbirds, and its fleshy blue or purple-black fruits are dispersed by birds. Nearly all Palicourea species are distylous; this appears to be the ancestral condition for the genus, and it seems to have been lost in peripheral, isolated populations of some species (Sobrevila et al., 1983) and some species on Caribbean islands (Taylor, 1993). In this traditional sense Palicourea has been studied primarily regionally (Steyermark 1972, 1974; Bacigalupo 1952; Burger & Taylor 1993; Jung-Mendaçolli et al 2007; Taylor 1989, 1993, 2000, Taylor et al. 2007) , and monographic work is in progress (Taylor, 1997).
However Palicourea is closely related to many neotropical species that have been included in Psychotria subg. Heteropsychotria Steyerm. (Steyermark, 1972), and in fact both morphological (Taylor, 1996) and molecular studies (Nepokroeff et al., 1999; Andersson, 2001; Andersson & Rova, 1999) show that Palicourea plus many of the species of Psychotria Subg. Heteropsychotria together comprise a monophyletic group. This expanded or combined group takes the name Palicourea, and is sometimes referred to as "Palicourea sensu lato". This group also includes many of the species formerly called Cephaelis. Traditionally these genera have been separated mainly by their flower form: species of Palicourea generally have colored flowers separated on developed pedicels, corollas with well developed tubes, abundant nectar, and other adaptations for hummingbird pollination; while species of Subg. Heteropsychotria generally have small white flowers borne in various arrangements and pollinated by insects. Also the genus Cephaelis was previously separated from Palicourea and Psychotria Subg. Heteropsychotria by its capitate inflorescences with well developed bracts. It now appears that the inflorescence and corolla characters are widely variable within this group, and that both hummingbird pollination and capitate inflorescences with involucral bracts have evolved several times within this group (Nepokroeff et al., 1999; Andersson, 2001; Andersson & Rova, 1999).
Much work remains to be done in understanding species identities and relationships before these genera can be united in a meaningful fashion. Some of the species of Psychotria subg. Heteropsychotria do not belong to Palicourea sensu lato and have been separated in several other genera, notably
Transfer of the remaining species from Psychotria subg. Heteropsychotria to Palicourea is now proceeding (Taylor & Gereau, 2010; Taylor, 2015), as the numerous individual species are studied and their circumscriptions and relationships clarified. The list of species of Palicourea below includes all the species that have been formally transferred to this genus. Accepted names in Palicourea are listed in bold-face type below, with synonyms listed in non-bold type. The infrageneric classification of each species is cited on its species project page along with notes about its identification and distribution.
The diversity of species and morphology, and in particular inflorescence arrangement, flower features, and display colors, is stunning in Palicourea and exploration of montane areas of Central and South America continues to discover new, morphologically unexpected species at a significant rate. Understanding of the component species and their features will be necessary to understand the factors that have stimulated this exceptional diversification in Palicourea. The wide variation in inflorescence and flower features in the group, including the range of display colors, suggests that diversification is related in good part to pollination adaptations, as proposed for a diverse montane group of Solanaceae that grows together with Palicourea and has generally similar flowers, pollination, and variation (Muchhala et al., 2014). Palicourea also includes a good amount of variation in infructescence arrangement and color, fruit size and color, and pyrene form, so adaptations for dispersal also probably play a role. As with any study of evoluationary patterns, a solid and reasonably comprehensive taxonomy of the study group is needed before its radiation can be accurately understood. This taxonomy is the current focus of my work.
Author: C.M. Taylor.
The content of this web page was last revised on 24 July 2015.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml